Effects of Electric Current
Q41. The bulb does not glow in the setup shown in Figure. List
the possible reasons. Explain your answer.
Image from NCERT
Ans. The bulb may not glow because of the following
The connections of wires in the circuit may
The bulb may be fused.
The battery may be used up.
The conductivity of liquid may be very low.
The liquid may be non-conductor of
Q42. The process that you saw in Activity 14.7 is used for
purification of copper. A thin plate of pure copper and a thick rod of impure
copper are used as electrodes. Copper from impure rod is sought to be transferred
to the thin copper plate. Which electrode should be attached to the positive
terminal of battery and why?
Ans. A thick rod of impure copper should be connected
to the positive terminal of the battery. A thin plate of pure copper should be
connected to the negative terminal of the battery. On passing electric current,
the metal dissolves from the impure anode and goes into the electrolyte
solution. The positively charged ions of metals present in their molten
compounds are attracted by the negatively charged electrode.
Q43. How would you classify lemon juice- a good conductor or a
poor conductor of electricity?
When the lemon juice between the two ends of the tester allows the electric current
to pass, the circuit of the tester becomes complete. The current flows in the
circuit and the bulb glows. This shows that lemon juice- a good conductor of
Q44. A beaker contains an acidified copper sulphate solution. A
copper plate and a carbon rod are kept in this copper sulphate solution. The
copper plate is connected to the positive terminal of a battery whereas the
carbon rod is connected to the negative terminal of the battery. What happens
when electric current is passed through copper sulphate solution?
Ans. When electric current is passed through the
copper sulphate solution, copper sulphate dissociates into copper and sulphate.
The free copper gets drawn to the electrode connected to the negative terminal
of the battery and gets deposited on it. From the other electrode, a copper plate,
an equal amount of copper gets dissolved in the solution. Thus, the loss
of copper from the solution is restored and the process keeps going. This means
that copper gets transferred from one electrode to the other.